JP2002226967A - Vapor deposition material for producing optical layer with high refractive index, and method for manufacturing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a vapor deposition material exhibiting excellent melting and evaporation behaviors, for an optical layer having a high refractive index. SOLUTION: The vapor deposition material for producing the high-refractive- index optical layer consisting of titanium oxide, titanium, and lanthanum oxide under reduced pressure is composed of a sintered mixture having a composition represented by TiOx+z(La2O3) (wherein, x is 1.5 to 1.8 and z is 10 to 65 wt.% on the basis of the total weight of the mixture). The mixture is constituted of 19-65 wt.% lanthanum oxide, 33-74% titanium oxide and 2-7 wt.% titanium. By this method, the use of the optical layer composed of this vapor deposition material as an antireflection layer to be formed on a spectacle lens, a lens for optical tool, and an optical element for laser technology and also as a layer having a preset high refractive index and/or optical absorption characteristics and used for a beam splitter, an interference mirror, a luminescence mirror and a heat insulating filter is made possible.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a vapor deposition material for producing a high refractive index optical layer of titanium oxide, titanium and lanthanum oxide under reduced pressure, and a method for producing the vapor deposition material.

[0002]

BACKGROUND OF THE INVENTION In the industry, especially in the optical industry, oxide layers are widely used as protective layers or for optical function purposes. They serve as protection against corrosion and mechanical damage, or for coating the surfaces of optical elements and devices such as lenses, mirrors, prisms, objectives and the like. In addition, oxide layers are used to produce high, medium and low refractive index optical layers to enhance or reduce reflection. The most important areas of application are the manufacture of antireflection layers on spectacle and camera lenses, binoculars and optical components, and optical components for laser technology. Further applications are e.g. interferometers, beam splitters,
The production of layers with special refractive index and / or specific optical absorption properties for heat filters and cold light mirrors.

[0003] DE 4208811 A1 discloses a vapor deposition material for producing a high refractive index optical layer by vapor coating a substrate under reduced pressure. This material has the formula La ₂ Ti ₂
It is a compound represented by O _{7- x} (where x is 0.3 to 0.7), particularly a compound represented by the formula La ₂ Ti ₂ O _6.5 . This type of vapor deposition material is produced by mixing lanthanum and titanium oxides and metallic titanium in corresponding stoichiometric ratios and sintering the mixture at a high vacuum below its melting point.

DE 1 288 489 discloses a thin oxide layer substantially free of absorption in the visible wavelength range for optical purposes, in particular on glass substrates, by the deposition of oxides and / or oxidizing substances under reduced pressure. Discloses a method for producing. If desired, the deposition can be performed under an oxidizing atmosphere. An oxide and / or oxidizing material is deposited on one or more elements and / or oxides from the group consisting of rare earths including yttrium, lanthanum and cerium. Where the starting materials are as a mixture,
Or evaporated away from each other. The oxides and / or oxidizing substances used are in particular titanium and / or titanium oxide.

[0005] For the production of high refractive index layers having an optical refractive index of about 2, the selection of suitable starting materials is limited. Possible starting materials for this purpose are essentially titanium, zirconium, hafnium and tantalum oxides, and mixtures thereof. A preferred starting material for the high refractive index layer is titanium dioxide.

In addition to titanium oxide, the prior art further comprises compounds such as tantalum oxide, zirconium oxide, hafnium oxide and zinc sulfide, and oxide mixtures,
For example, zirconium oxide and titanium oxide, titanium oxide and praseodymium oxide, and titanium oxide and lanthanum oxide are used.

These materials have the advantage that, for example, titanium dioxide has a high refractive index and hafnium oxide and zirconium oxide have a low absorption. Disadvantages of these known materials are vigorous gas evolution and titanium dioxide spitting, tantalum oxide T
relatively high absorption in the case of a ₂ O _{5 and in} the case of mixtures of titanium oxide and praseodymium oxide, and incomplete dissolution of zirconium oxide, hafnium dioxide and mixtures of zirconium oxide and titanium dioxide; Low hardness as in the case of In the case of a mixture of titanium oxide and lanthanum oxide, the advantages of low absorption, no gas evolution and no blowing, and relatively good dissolution are achieved. However, the refractive index of this type of mixture is much lower than for titanium dioxide and zinc sulfide. From the point of view of practical processing, it is also disadvantageous that these substances have a high melting point and a boiling point, which are relatively close to each other. In order to ensure a uniform and adequate evaporation rate, the deposited material must be completely dissolved before strong evaporation starts. This condition is necessary so that a layer of uniform and uniform thickness can be formed on the object to be coated by vapor deposition. However, this is not the case under practical use conditions for zirconium and hafnium oxides, but is the case for titanium / zirconium mixed oxide systems. The materials do not melt or do not completely melt under typical processing conditions, are difficult to evaporate entirely, and cause thickness changes in the deposited layer. The purpose of the prior art is to lower the melting point of the base material with suitable additives, which further change the refractive index of the resulting layer within certain limits,
Helps to set the refractive index to a specific value. The choice of an appropriate additive for this purpose is limited by the need to eliminate absorption. Accordingly, the only metal oxides suitable as corresponding additives are those that do not absorb in the visible spectral region to the near ultraviolet wavelength region, ie, up to about 320 nm.

As starting materials, the oxides show no or only slight absorption in the visible wavelength range, which is a fundamental requirement for the corresponding optical applications. However, oxygen deficiency and the deposition of sub-equivalent titanium oxide layers with respect to oxygen content occur during high vacuum evaporation. This means that, without using special precautionary measures, the production of thin layers by vacuum evaporation of these materials results in layers having a high absorption in the visible region. According to German Patent 1,288,489, this problem is solved by establishing a specific residual oxygen pressure of 5 × 10 ⁻⁵ <5 × 10 ⁻⁴ mbar, ie an oxidizing atmosphere, and performing the evaporation under reduced pressure. You. Another possibility for solving this problem consists in subjecting the resulting layer to postconditioning in oxygen or air.

[0009] Even though the above problems can be solved by the proper choice of additives or the selection of the corresponding substance mixtures, the use of mixed systems is itself not preferred in the vacuum deposition technique. The reason is that the mixed system usually evaporates inconsistently, ie changing the composition during the evaporation process, and the composition of the deposited layer correspondingly. This can be avoided if the mixed system consists of separate chemical compounds that evaporate and re-condense without changing the material.

[0010]

SUMMARY OF THE INVENTION It is an object of the present invention to provide an optical layer having the highest possible refractive index and low absorption, from which the deposited material exhibits very good melting and evaporation behavior. It is an object of the present invention to provide a vapor deposition material of the type mentioned at the outset, which can be evaporated substantially without gas generation or ejection.

[0011]

SUMMARY OF THE INVENTION The object of the present invention is to make the material TiO _x + z (La ₂ O ₃ ) (x is 1.5 to 1.8, z is 10 to 65% by weight based on the total weight of the mixture). This is achieved by the invention which is a sintered mixture having

[0012]

DETAILED DESCRIPTION OF THE INVENTION In one embodiment of the present invention, the mixture comprises 19-65% by weight lanthanum oxide, 33-74% by weight titanium oxide and 2-7% by weight titanium. In a particular embodiment of the invention, the mixture consists of 58.9% by weight of lanthanum oxide, 37.9% by weight of titanium oxide and 3.2% by weight of titanium. An embodiment is likewise proposed in which the mixture consists of 63.2% by weight of lanthanum oxide, 33.9% by weight of titanium oxide and 2.9% by weight of titanium. In addition, the lower limit of titanium oxide can be set to 38% by weight.

In one embodiment of the present invention, the ratio of titanium oxide TiO ₂ to titanium determines the stoichiometry for oxygen in titanium oxide TiO _x where x is between 1.5 and 1.8. The weight ratio of titanium oxide: lanthanum oxide can be determined by mixing lanthanum oxide with a mixture of titanium oxide and titanium. Sintering under reduced pressure ensures that the stoichiometry of the mixture with respect to oxygen does not change. The vapor deposition material of the present invention has an oxygen deficiency within the above formula definition as compared to the base compound lanthanum titanate having the correct stoichiometric composition. Due to the deliberate establishment of oxygen vacancies in the deposition material according to the invention, a further release of oxygen, which during evaporation under reduced pressure leads to an undesired blowing of the molten deposition material, firstly takes place. Next, the selection range of oxygen deficiency is such that a layer that does not show absorption under normal processing conditions in vacuum evaporation is automatically formed. Studies have shown that relatively low loadings of lanthanum oxide can improve the behavior during melting and evaporation. By setting the optimal stoichiometry with respect to oxygen, the mixture of the present invention can be melted and vaporized in an electron beam evaporator without substantial blowing and gas generation. Here it can be seen that the optical properties of the resulting layer are not substantially affected by changes in the residual oxygen pressure during evaporation under reduced pressure. On the other hand, in the case of titanium oxide (IV) TiO ₂ and also in the case of titanium suboxide such as TiO _1.7 , Ti ₃ O ₅ or Ti ₄ O ₇ , blowing during melting cannot be completely prevented. Can not. The refractive index of the layers produced using the vapor deposition material of the present invention is slightly lower than for a pure titanium oxide layer. In particular, the index of refraction is significantly higher for layers of tantalum oxide, zirconium oxide, hafnium oxide or oxides, for example layers of zirconium oxide and titanium oxide, titanium oxide and praseodymium oxide, and titanium oxide and lanthanum oxide. Excellent melting behavior allows a flat melting surface to be established and maintained for evaporation of the deposited material. This makes it possible to set a uniform reproducible layer thickness distribution on the substrate to be coated. This is very difficult or impossible, especially when using materials with poor melting behavior, for example hafnium oxide, zirconium oxide or a mixture of zirconium oxide and titanium oxide.

It is a further object of the present invention to provide a method which allows the production of vapor deposited materials which can be converted into high refractive index optical layers without blowing and gassing. This is because the composition TiO _x + z (La
₂ O ₃ ) (x is 1.5 to 1.8, z is 10 to 65% by weight based on the total weight of the mixture), and a mixture of titanium oxide, titanium and lanthanum oxide is uniformly mixed, and the particle size is 1
This is achieved by granulating or tableting to ４4 mm, followed by sintering under reduced pressure. When performing this method, sintering is performed at a temperature of 1500-1600 ° C. and 1 × 1.
It is carried out under reduced pressure of 0 ^-4 mbar for 5.5 to 6.5 hours.

A further object is to provide a method which allows the production of an optical layer having a high refractive index and substantially no absorption from the deposited material. This involves cleaning the substrate to be coated, drying it, placing it on a substrate holder in a deposition unit, depressurizing the deposition unit to 1 × 10 ⁻⁵ mbar and heating the substrate to 280-310 ° C. , 1-2 × 10 ^-4 mbar
Oxygen into the deposition unit until a pressure of
The material was melted in an electron beam evaporator in a vapor deposition unit sealed by a screen, heated to its evaporation temperature of about 2200-2300 ° C., and after opening the screen, the substrate was predetermined with the vapor deposition material. Achieved by a method of coating to thickness. A refractive index of 2.1 at a wavelength of 500 nm;
An optical layer of the deposited material of 5 to 2.25, in particular 2.20, is obtained. Optical layers of this type are prevalent, as anti-reflective layers on spectacle lenses, lenses for optical tools, optical components for laser technology, and beam splitters,
Used as a layer with preset high refractive index and / or optical absorption properties for interference mirrors, cold light mirrors and thermal filters.

Using the vapor deposition material of the present invention to produce a homogeneous thin layer of uniform thickness with strong adhesion and particularly resistant to mechanical and chemical influences on a suitable substrate. Can be. As mentioned above, these layers have high refractive indices and typically have high transmittance in the near ultraviolet, that is, in the wavelength range from about 360 nm to near infrared at about 7000 nm beyond the visible range. These optical layers exhibit substantially no absorption in the visible wavelength region.

[0017]

The invention will be described in more detail with reference to two examples, which are in no way limiting of the inventive concept.

EXAMPLE 1 A mixture of 58.9% by weight of lanthanum oxide, 37.9% by weight of titanium oxide and 3.2% by weight of titanium was mixed homogeneously, granulated to a particle size of about 1 to 4 mm, and reduced under reduced pressure to about 1 to 4 mm. 6 at 1500 ° C
Bake for hours. The calcined product is dark black.

To produce an optical layer, the sintered product is
It is introduced into a molybdenum crucible in a vapor deposition unit and inserted into the electron beam evaporator of the unit. For example, a substrate to be coated, such as a quartz glass disk having a diameter of 25 mm and a thickness of 1 mm, is cleaned and dried, and placed on a substrate holder in a vapor deposition unit. The vapor deposition unit is a unit known from the prior art, and is not shown or described in detail. 1x1
After evaporating to a pressure of 0 ⁻⁵ mbar, the substrate is heated to about 300 ° C.
Heat to a temperature of Next, oxygen was added to 1-2 × 10 ⁻⁴ mb.
Ar enters the deposition unit via a control valve until a pressure of ar is achieved. The deposition material is melted under the screen of the electron beam evaporator and heated to an evaporation temperature of 2200 ° C. As soon as this evaporation temperature is achieved, the screen is opened and the substrate is coated with the desired thickness of the optical layer. After cooling, the coated substrate is taken out of the vapor deposition unit. The transmittance of the layer was determined using a spectrophotometer. 2.20 refractive index at 500 nm wavelength
Was determined from the transmittance curve. The thickness of the layer was 267 nm.

Example 2 A mixture of 63% by weight of lanthanum oxide, 34% by weight of titanium oxide and 3% by weight of titanium was homogeneously mixed, and the particle size was about 1 to 4 m.
and calcined under reduced pressure at about 1500 ° C. for 6 hours. The calcined product is dark black.

An optical layer of a sintered deposition material was manufactured in the same manner as described in Example 1. These optical layers are
The refractive index at 500 nm was 2.16. The thickness of the optical layer was 271 nm. The layers are visible and 9
It showed no absorption at wavelengths up to 00 nm.

 ──────────────────────────────────────────────────続 き Continuation of front page (71) Applicant 591032596 Frankfighter Str. 250, D-64293 Darmstadt, Federal Republic of Germany (72) Inventor, Anthes, Uwe, Germany 64271 Darmstadt Merck Inside Kargaea (no address) (72) Inventor, Fritz, Martin, Germany 64271 Darmstadt Merck Inside the car game arc (No address) F-term (reference) 2K009 AA02 CC03 DD03 4K029 BA50 BC07 BD00 CA01 DB05 DB21 EA01

Claims (11)

[Claims] 1. A deposition material for producing a high refractive index optical layer of titanium oxide, titanium and lanthanum oxide under reduced pressure, wherein the material is composed of TiO _x + z (La ₂ O ₃ ) (x
Is 1.5 to 1.8, and z is 10 based on the total weight of the mixture.
(65% by weight). 2. The vapor deposition material according to claim 1, wherein the mixture contains 19 to 65% by weight of lanthanum oxide, 33 to 74% by weight of titanium oxide and 2 to 7% by weight of titanium. 3. The vapor deposition material according to claim 2, wherein the mixture consists of 58.9% by weight of lanthanum oxide, 37.9% by weight of titanium oxide and 3.2% by weight of titanium. 4. The vapor deposition material according to claim 2, wherein the mixture comprises 63% by weight of lanthanum oxide, 34% by weight of titanium oxide and 3% by weight of titanium. 5. The method according to claim 1, wherein the ratio of titanium oxide TiO ₂ to titanium is:
The vapor deposition material according to claim 1, wherein a stoichiometry for oxygen in titanium oxide TiO _{x where} x = 1.5 to 1.8 is determined. 6. The vapor deposition material according to claim 1, wherein the weight ratio of titanium oxide: lanthanum oxide can be determined by mixing lanthanum oxide with a mixture of titanium oxide and titanium. 7. The method according to claim 1, wherein the optical layer of the vapor-deposited material has a refractive index of 2.15 to 2.25, particularly 2.20, at a wavelength of 500 nm. Evaporation material. 8. The method for producing a vapor deposition material according to claim 1, wherein the composition TiO _x + z (La ₂ O ₃ ) (x is 1.5 to 1.8, and z is the total weight of the mixture) 10 to 10
(65% by weight), and a mixture of titanium oxide, titanium and lanthanum oxide is uniformly mixed, granulated or tableted to have a particle size of 1 to 4 mm, and then sintered under reduced pressure. Method. 9. The method according to claim 8, wherein the sintering is performed at a temperature of 1500 to 1600 ° C. under a reduced pressure of 1 × 10 ⁻⁴ mbar for 5.5 to 6.5 hours. . 10. A method for producing an optical layer of a vapor deposition material according to claim 1, wherein the substrate to be coated is cleaned,
After drying, the substrate was placed on a substrate holder in the vapor deposition unit, the pressure of the vapor deposition unit was reduced to 1 × 10 ⁻⁵ mbar, and
Heat to 0-310 ° C., put oxygen into the evaporation unit until a pressure of 1-2 × 10 ⁻⁴ mbar is achieved, melt the evaporation material in an electron beam evaporator in the evaporation unit sealed by a screen Heating the material to its evaporation temperature of about 2200 to 2300 ° C., opening the screen, and coating the substrate with a vapor deposition material to a predetermined thickness. 11. Preset high refractive index as an anti-reflective layer on spectacle lenses, lenses for optical tools, optical elements for laser technology, and for beam splitters, interference mirrors, cold mirrors and thermal filters. Use of an optical layer manufactured according to claim 10 as a layer having optical absorption properties.